Spiro[cyclopropane-1,2'-indolin]-3'-ones of the general formula: ##STR1## wherein the ring A is a substituted or unsubstituted phenyl ring and Z is hydrogen, a substituted or unsubstituted alkyl group or a substituted or unsubstituted acyl group and their pharmaceutically acceptable salts have gastric acid secretion suppressing activity, antiinflammatory activity and analgesic activity.
A spirocompound, 1'-acetylspiro [cyclopropane-1, 2'-[2H] indol]-3'(1'H)-one (III-1), was synthesized from anthranilic acid in three steps, which involve the condensation of anthranilic acid with α-bromo-γ-butyrolactone, followed by spiroannelation with acetic anhydride and triethylamine, and subsequent decarboxylation in the presence of sodium chloride to afford III-1 in good yield. Various derivatives (III-2-III-9) were similarly prepared. Some compounds of this series showed an intense fluorescence in solution. The reactivities of III-1 to electrophiles and nucleophiles, as well as its reaction with reducing agents, were investigated.